Vulcanization of elastomeric olefinic copolymers with organic diperoxides



United States Patent O lint. Cl. G08f 15/04 U.S. Cl. 2608S.2 15 ClaimsABSTRACT OF THE DISCLOSURE Vulcanizable composition of (1) avulcanizable polymer which is either a saturated elastomeric copolymerof ethylene with a higher alpha-olefin having the formula OH =CHR inwhich R is a lower alkyl radical, the copolymer having an ethylenecontent of from about 5 to 70 mol percent, or a low unsaturationterpolymer of ethylene with propylene or butene-l and with a cyclicnon-conjugated polyene, the terpolymer having an ethylene content offrom about 20 to 80 mol percent and a polyene content of from about 0.1to 20 mol percent, the molecular weight of the polymer being betweenabout 60,000 and 800,000; (2) a diperoxide having the general formula:

in which R to R inclusive, are selected from the group consisting ofunsubstituted and halogen-substituted lower alkyl radicals, R and R areselected from the group consisting of unsubstituted and substitutedalkyl radicals containing from 1 to 6 carbon atoms and unsubstituted andsubstituted aromatic radicals containing from 6 to 20 carbon atoms, andA is an arylene radical selected from the group consisting of phenylene,diphenylene and naphthylene, in a concentration of from about 0.002 to0.02 mol of diperoxide per 100 grams of the vulcanizable copolymer orterpolymer; and (3) a radical acceptor selected from the groupconsisting of sulfur, quinone compounds and dimaleimidic compounds, in aconcentration of from 0.1 to 20 grams per 100 grams of the vulcanizablecopolymer or terpolymer.

Process for vulcanizing this composition comprising homogenizing it andvulcanizing at a temperature of from about 110 C. to 260 C. Particularlyrapid vulcanization rates may be obtained at temperatures of from about200 to 250 or 260 C.; such high temperature vulcanizations may beconducted in an injection press or in a liquid eutectic salt mixture.

CROSS-REFERENCE TO RELATED APPLICATION This application is acontinuation of application Ser. No. 628,230, filed Mar. 30, 1967, nowabandoned which latter application is in turn a continuation-in-part ofapplication Ser. No. 160,665, filed Dec. 19, 1961, now abandoned.

BACKGROUND OF THE INVENTION Field of the invention The present inventionrelates to the use of new organic 3,522,225 Patented July 28, 1970 "icediperoxides in the vulcanization of olefin copolymers and to methods forpreparing the new diperoxides.

Description of the prior art It is known that organic monoperoxides areuseful as generators of free radicals and, therefore, as initiators offree-radical polymerization reactions.

Another peculiar characteristic of peroxidic substances is that theyare, in general, good cross-linking agents for vulcanization mixescontaining natural and synthetic copolymers. The products generally usedfor this purpose contain in their molecules .a peroxidic function,-O-O--, and have the general formula:

in which the R radicals are aryl, alkyl, substituted aryl, orsubstituted alkyl radicals, hydrogen, ether radicals, cycloalkylradicals, etc.

Many of these monoperoxides have a relatively high vapor pressure whichresults in their loss by evaporation, to a certain extent, duringcompounding and storage of the mixes.

There are also known some other types of peroxides which contain intheir molecule two peroxidic groups and have a low vapor pressure, forexample, substances having the following general formulae:

in which the R radicals are the same or different hydrocarbon residues.When such diperoxides are used in the vulcanization of saturatedcopolymers, e.g., copolymers of ethylene with propylene and/or butene,all of said diperoxides show a cross-linking effectiveness whichcorresponds at most to the effectiveness of the same molar concentrationof a monoperoxide (e.g., dicumyl peroxide), that is, as if only oneperoxidic radical were present in the molecule.

SUMMARY OF THE INVENTION The present invention provides vulcanizablecompositions comprising elastomeric copolymers of ethylene and newperoxidic compounds characterized by the presence of two peroxidicgroups, OO, in their-molecule and by a relatively low vapor pressure,and which are highly efiective vulcanizing agents for vulcanizablepolymers, as well as a process for vulcanizing these compositions.

More particularly, the present invention provides a vulcanizablecomposition comprising (1) a vulcanizable polymer selected from thegroup consisting of (a) a saturater elastomeric copolymer of ethylenewith a higher alpha-olefin having the formula CH =CHR in which R is alower alkyl radical, said copolymer having an ethylene content of fromabout 5 to 70 mol percent and (b) a low unsaturation terpolymer ofethylene with propylene or butene-l and with a cyclic or acyclicnon-conjugated polyene, said terpolymer having an ethylene content fromabout 20 to mol percent and a polyene content of from in which R to Rinclusive, are selected from the group consisting of unsubstituted andhalogen-substituted lower alkyl radicals, R and R are selected from thegroup consisting of unsubstituted alkyl radicals containing from 1 to 6carbon atoms and unsubstituted and substituted aromatic radicalscontaining from 6 to carbon atoms, and A is an arylene radical, selectedfrom the group consisting of phenylene, diphenylenea nd naphthylene, ina concentration of from about 0.002 to 0.02 mol of diperoxide per 100grams of said vulcanizable copolymer or terpolymer; and (3) a radicalacceptor selected from the group consisting of sulfur quinone compoundsand dimaleimidic compounds, in a concentration of from 0.1 to 20 gramsper 100 grams of the vulcanizable copolymer or terpolymer.

The present invention also provides a vulcanization process whichcomprises homogenizing the above composition and vulcanizing it at atemperature of from about 110 C. to 260 C.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred copolymers forvulcanization in accordance with the present invention include thelinear rubbery copolymers of ethylene with propylene and/or butene-l inwhich ethylene is present in an amount of from about 5 to 70%,preferably to 65%, by weight and which are substantially amorphous asdetermined by X-ray diffraction.

Preferred low unsaturation terpolymers include polymers of ethylene withpropylene and/or butene-l and with acyclic or acyclic polyene havingnon-conjugated double bonds. Polyenes which are particularly suitablefor use in preparing the terpolymers include pentadiene-l,4,hexadiene-l,4, hexadiene-1,5, heptadiene-l,5, dodecatriene-1,7,9,S-methylen-norbornene, norbornadiene-2,5, 2- alkylnorbornadiene-2,5,cyclooctadiene-l,5, dicyclopentadiene, 4,7,8,9-tetrahydroindene,5-methyl-4,7,8,9-tetrahydroindene, 5,6 dimethyl4,7,8,9-tetrahydroindene, etc. Particularly preferred vulcanizableterpolymers inlcude theethylene/propylene/5-methyl-4,7,8,9-tetrahydroindene andethylene/butene-l /5-methyl-4,7,8,9-tetrahydroindene terpolymers.

The molecular weight of the vulcanizable copolymer or terpolymer may beof the order of between about 60,000 and about 800,000, preferablybetween about 70,000 and 500,000.

A particularly important feature of the present invention is thediscovery that, surprisingly, both peroxidic groups, -OO, of the newdiperoxides participate in the cross-linking, so that the cross-linkingeffectiveness for the polymer is, at the same molar concentration,almost twice that of the most effective monoperoxides of the prior art.

The cross-linking takes place through a thermal breakdown into four freeradicals all of which are capable of abstracting hydrogen from thepolymer chains without undergoing undesired side reactions of anyappreciable extent.

In comparison with the conventional monoperoxides With the sameperoxidic oxygen content, the diperoxides of the present invention alsohave the advantage that they do not have the high volatility which istypical of the low molecular weight monoperoxides and can be used at theusual working temperatures Without any appreciable evaporation from themass.

Moreover, due to the low volatility and good crosslinking efficiencyeven at high temperature of the new diperoxides, the compositions of thepresent invention can be vulcanized at temperatures considerably higherthan those heretofore employed in the conventional vulcanization press,these higher temperatures being in the range of from about -269 C. Greateconomic advantage is afforded by these vulcanization temperaturesinasmuch as the vulcanization time is thereby sharply reduced.

In addition, in accordance with a particularly preferred feature of thepresent invention, the high temperature vulcanization may be conductedin an injection press or a. eutcet c salt mixture, e.g., Du Ponts Hitec,comprising 40% NaNO 7% NaNO and 53% KNO The vulcanization process may beperformed also as a continuous process by extruding the vulcanizablecomposition of the inventions, and passing the extrudate through theeutetic salt mixture at a temperature of from about 180 to 260 C.,preferably 200 to 260 C., more preferably 205 to 250 C., for from about30 seconds to 6 minutes. This continuous high temperature vulcanizationprocess affords a great economic advantage in markedly reducing both thevulcanization time and waste. In addition, it is possible to moreaccurately control the size and shape of the vulcanizates, and to avoiddeformation of even thin delicately shaped extrudates duringvulcanization, while at the same time obtaining bright surfaces. I

In addition to the fact that both peroxidic functions are involved inthe vulcanization, the new diperoxide compounds exhibit stability toheat and impact, which stability, however, does not impair theircapacity to form free radicals.

The diperoxides of the present invention have the general formula:

in which R and R are lower alkyl radicals in which the hydrogen atomsmay be partially substituted with halogens; R and R are selected fromthe group consisting of lower alkyl radicals containing from 1 to 6carbon atoms in which the hydrogen atoms may be partially substitutedwith halogens, and aromatic radicals containing from 6 to 20 carbonatoms in which the hydrogen atoms may or may not be substituted withalkyl, aryl or cycloalkyl radicals or with halogens; and A is an aryleneradical selected from the group consisting of phenylene, diphenylene ornaphthylene. According to a preferred feature of the invention, R to Rcontain from 1 to 6 carbon atoms and, more preferably, are methylgroups.

For preparing the organic diperoxides of the invention, it has beenfound particularly useful to react an organic hydroperoxide 1) With ahydrocarbon containing two mobile hydrogen atoms in the presence of acatalyst which is a transition metal salt of the kind used in the methodof Kharasch et al. (J. Org. Chem. 24, 72, l959); or

(2) With an alkyl carbinol containing two tertiary alcohol functions inthe presence of an acid condensing agent.

In the first alternative process, the reaction of the hydroperoxide withthe hydrocarbon takes place according to the scheme:

In this process, however, the organic hydroperoxide must be introducedgradually, at a controlled rate and at the reaction temperature, intothe agitated catalyst-hydrocarbon mixture.

The conventional method of preparing monoperoxides, in which a mixtureof the two main reactants is heated in the presence of the catalyst (seethe aforementioned work of Kharasch et al.), cannot be used because ofthe strong and uncontrollable reactions which occur. The separation ofthe diperoxides thus obtained from the reaction mixtures is carried outby evaporation under vacuum, fractional crystallization, or in any othersuitable way.

Preferably, the separation is carried out by washing the reactionmixture with dilute acid solution. Two layers form as a result of suchwashing, an aqueous layer and a non-aqueous layer. The aqueous layercontains the catalyst and the water soluble products; the non-aqueouslayer in which the diperoxide is dissolved is separated easily from theaqueous layer, and is subjected to a vacuum distillation to remove otherwater insoluble by-products. If desired, the residue containing thediperoxide may be further purified by solvent crystallization or byanother method such as counter-current solvent partition or bychromatographic separation.

Organic hydroperoxides which may be used include: tert-butylhydroperoxide, -oc,oa' dimethyl benzylhydroperoxide,aged-dimethyl-phenyl-benzylhydroperoxide, o,oc'iSO-propylnaphthyl-hydroperoxide and the like.

As the hydrocarbon containing two mobile hydrogen atoms, there may beused, for example, diisopropyl benzene, diisopropyl diphenyl,diisopropyl naphthalene, diisopropyl anthracene, diisopropyl terphenyl,diisopropyl tetrahydronaphthalene, diisobutyl benzene, diisoamylbenzene, diisobutylnaphthalene and the like.

Suitable catalysts include, e.g., halides of Cu, Mn and Co andmetalorganic compounds such as Cu-dodecylbenzene sulfonate,Co-acetylacetonate and Co-naphthenate. Preferred catalysts includecopper chloride and manganese chloride.

At least 4 mols of organic hydroperoxide are used per mol ofhydrocarbon.

The organic hydroperoxide and hydrocarbon are reacted at a temperatureof from about 40 C. to 120 C., preferably from about 70 to 90 C.

In the second alternative process for preparing the organic diperoxides,the hydroperoxide, which may be represented by the formula:

is reacted with a tertiary dialcohol having a central nucleus A, whichmay be represented by the formula:

(wherein R R R R and A are as defined above) according to the scheme:

The reaction is carried out by dissolving or suspending the teritarydialcohol (2) and the hydroperoxide (1) in an alcohol, ketone or strongorganic acid, and by adding an acid condensing agent to the solution orsuspension while agitating, at temperatures between about 0 C. and 80 C.

Generally, one mol of the alcohol is reacted with at least two mols ofthe hydroperoxide.

Preferably, the strong organic acid is propionic acid or acetic acid,while the acid condensing agent is selected from the group consisting ofperchloric acid, H 80 benzenesulfonic acid and boron trifluoride.

The aryl aridcal of the tertiary dialcohol may be benzene, diphenyl,naphthalene, anthracene or the like.

Outstanding and unpredictable advantages are obtained by using the newdiperoxidic compounds in the vulcanization of synthetic polymers and ofnatural rubber.

The saturated copolymers of ethylene with higher alphaolefins such aspropylene and/or butene-l as well as the low unsaturation tempolymersare vulcanized by using, as cross-linking agents, the organicdiperoxides together with an auxiliary vulcanizing aid acting as aradical acceptor; this radical acceptor is selected from the groupconsisting of sulfur, quinone compounds and dimaleimidic compounds andis used in amounts from 0.1 to 20 parts by weight per parts of copolymeror terpolymer. Sulfur is the preferred auxiliary aid. We have found thatthe use of a small amount of sulfur together with the diperoxidesgreatly increases the eifectiveness of said diperoxides as vulcanizationagents.

The most remarkable advantages obtained by using the present newdiperoxides in the vulcanization of mixes containing olefin polymers canbe summarized as follows:

(1) The possibility of using the new diperoxides in lowerconcentrations, to obtain vulcanized products having the samecharacteristics;

(2) The possibility of vulcanizing at higher temperatures than thoseheretofore employed, to thereby markedly reduce the vulcanization time;

(3) The reduction of the residual odor in the vulcanized product as aconsequence of the lower concentration of vulcanizing agent which can beused efficiently, and of the lower volatility of the by-productsthereof;

(4) Easy mixing of the diperoxides with rubbery polymers due to thecrystalline character of the new diperoxides and their very lowvolatility;

(5) Absence of scorching due to the relatively high decomposition pointof the diperoxides;

(6) Good vulcanization rate at the temperatures normally used in therubber industry;

(7) Vulcanization homogeneity, due not only to the absence of scorching,but also to the relatively low melting point and to the solubility ofthe new diperoxides in the molten polymers;

(8) The possibility of using additives commonly used in the rubberindustry, such as carbon black, silica, clay, plasticizers, etc.,without altering the greater vulcanizing effectiveness of the newdiperoxides.

The vulcanizable mixtures of the present invention can be prepared inany apparatus commonly used for mechanical mixing in the rubberindustry. The vulcanization can be carried out advantageously in theapparatus commonly used in the rubber industry for heating and shapingpurposes.

The diperoxide concentration essentially depends upon thecharacteristics desired for the vulcanized products and is usuallybetween 0.002 and 0.02 mol of peroxide per 100 g. of the copolymer orterpolymer to be vulcanized.

Usually, the vulcanization can be carried out in a reasonable time attemperatures of from to 260 C., preferably, from to 200 C. A remarkablereduction in vulcanization time is achieved in accordance with apreferred embodiment employing temperatures of the order of about 200 to260 C., preferably, 205 to 250 C.

Excellent vulcanization results are obtained when the concentration ofsulfur to diperoxide is from about 0.6 to 3, preferably from about 1.6to 2.0, gram atoms of sulfur per mol of diperoxide. Obviously, this doesnot exclude the use of sulfur concentrations not within said range, forparticular purposes.

When auxiliary substances are added not only for their protective effectbut also in order to reinforce or modify the mechanical properties ofthe vulcanized products, as in the case of diene polymers having a vinylunsaturation, and of vinyl monomers, the concentration, which can varywithin wide limits, is determined by the particular effects to beachieved.

The diperoxides of the present invention are useful, also, for thevulcanization of other saturated or unsaturated elastomers generally,provided the latter can be vulcanized with organic peroxides. The newdiperoxides can be used in admixture with each other or withmonoperoxides. Moreover, they can be added to rubber either alone ormixed or diluted with inert material in the form of powder, paste or asolution.

The following examples illustrate the present invention without limitingits scope.

EXAMPLE 1 Into a 1000 cc. flask provided with an agitator, thermometer,reflux condenser and an inlet cock funnel, 162 g. of p-diisopropylbenzene and 8 g. CuCl were introduced under nitrogen.

The mixture was heated to 7580 C. while agitating under nitrogen, andthen, while maintaining this temperature, 490 g. of73%-tert.butyl-hydroperoxide were gradually added over a period of 20hours.

After the addition was completed, the agitation and heating werecontinued until almost all the hydroperoxide (at least 90%) disappeared.

While still maintaining the 7580 C. reaction temperature, 200 cc. of anaqueous solution containing 3% HCl were added. Two layers Were formed.The lower aqueous layer was discarded and the upper layer washed, whilewarm, with water until it was neutralized. It was then subjected tovacuum distillation at a pressure of 15/20 mm. of mercury and atemperature of 78-80 C. to eliminate the volatile substances. From theresidue, by methanol crystallization, there were obtained 140 g. of acrystalline substance having a melting point of 7576 C. andcorresponding to the formula:

(a,a.'-bis (tert.butyl peroxy)-p-diisopropylbenzene).

The analytical data agree with the aforementioned formula and are asfollows:

carbon content (C%)=17.32% (calculated:70.96%);

hydrogen content (H% )=9.81% (calculated=l0.13%

cryoscopic molecular weight (M.W.), found=338 (calculated=338.51).

EXAMPLE 2 0.2 g. of perchloric acid were added to a solution of 19.4 g.of (a,u-dihydroxy)diisopropylbenzene (melting point 142 C.) in 40 cc. ofglacial acetic acid and 24.1 g. of 75% tert.butyl hydroperoxide, kept atroom temperature. After a few minutes, a crystalline substanceprecipitated and was then isolated by filtration after dilution withwater.

28.5 g. a,a'-bis (tert.butylperoxy)-1,4-diisopropylbenzene, having thecharacteristics of the product described in Example 1, were obtained.

EXAMPLE 3 By operating in a manner similar to that described in Example1, but using alpha-cumyl hydromroxide instead of tert. butylhydroperoxide, the product corresponding to the formula cc,ot'-biS(cumyl peroxy)-p-diisopropylbenzene:

8 was obtained. It is a pale amber colored liquid having the followingcharacteristics:

Density at 20 C. 1.008

Refractive index n 1.5318

Active substance content, percent 57 EXAMPLE 4 To an agitated suspensionof 238.4 g. of a mixture of diisopropyldiphenyl isomers and 8 g. ofcuprous chloride, at a temperature of C., 480 g. of tert.butylhydroperoxide (75 solution) were added over 3 hours.

The agitation and the heating were continued for an additional 3 hoursand, after cooling, the catalyst was separated by filtration undervacuum. The filtrate was then concentrated at C. and at a pressure of0.5 mnr/Hg. 319 g. of a viscous liquid having the followingcharacteristics were obtained:

The liquid contained 64.7% oc,oc'-biS (tertbutylperoxy)diisopropyl-diphenyl:

Proceeding as in Example 4, but using diisopropyldiphenyl and cumylhydroperoxide, the following product was obtained:

aged-bis (cumyl peroxy) diisopropyl-diphenyl.

Density at 20 C. 1.058 Refractive index 12 1.5723

EXAMPLE 6 Analogously, using 2,S-diisopropylnaphthalene and tert. butylhydroperoxide, the following product was obtained:

CH3 CH3 CHa( 1CH3 H3 oc,tx'-bi$ (tert.butylperoxy)-2,5-diisopropylnaphthalene.

EXAMPLE 7 From an ethylene-propylene copolymer, containing 45% by molsof propylene and having a Mooney viscosity of 50 ML (1+4) at C., thefollowing mixes (Table I) were prepared in a roll mixer and were thenvulcanized in a steam press in the form of sheets having the dimensionsx 120x 2 mm.

From these sheets, C-type test pieces (ASTM D-412) were cut andsubjected to tensile tests in an Amsler-type dynometer with a rate ofseparation of the grips of 500 mm. per minute, to determine the tensilestrength, elongation at break and modulus at 300%. The residualelongation was determined on special specimens having a useful EMMPLE 9portion of 5 cm., kept for 1 hour under a tension with an elongation of200% and measured 1 minute after re- An ethylene-propylenebuteneterpolymer contammg leasing. 5% by mols of butene and 38% by mols ofpropylene Th lt are given i th lower part f T bl I, and having avisocsimetric average molecular weight of TABLE I a b c d e f h tEthylene propylene copolymer, g 100 100 100 100 100 100 100 100 100Carbon black HAF, g 50 Sulfur, gram-atoms Cumyl peroxide, mols 2,5-bis(tert.butyl perox imethylhexane (V arox a,a-bis(tert.butylperoxy)p-diisopropylbenzene, mols. a,a-bis(cumyl peroxy)diisopropylbenzene, mols- Mooney scorch time at 165 Characteristics ofthe vulcanized products (60 min. at 165 C Tensile strength, kg./cm. 187130 185 210 19s 65 100 112 114 Elongation at break, percent. 395 630 390410 405 410 450 420 410 Modulus at 390%, k ./em. 128 48 130 120 124 50 s69 67 Residual elongation at 200%, percent 6 20 6 6 5. 38 22 21 It isevident from Table I that the diperoxides of the 160,000, was vulcanizedas in Example 7. The results are present invention, a,or-bis(tert.butylperoxy) p-disoproreported in Table III.

pylbenzene and a,a-bis(cumyl peroxy)-diisopropylben- 25 zene, have avulcanizing effectiveness twice as high as TABLE III that ofmonoperoxides (e.g., cumyl peroxide) and of the known conventionaldiperoxide (e.g., 2,5-bis (tert.butyl gm 2g gg peroxy)2,5-dimethylhexane). guig rk r m n msu.5 n 0.00962 0.00962 0.00962 5-ser.uyperoxy-,5- e y From an examination of the mechanical characteris'hemneWamx) mols 0.00481 (Loom ties the vulcanized products, it appearsthat the products or,a-ll sis(eumylperoxy) diisopropylbenzene, 0 00481n10 obtamed from.mn.ms d and 8 present i Same de Characteristics oi theproducts, vulcanized gree of vulcanization (see modulus, elongatlon atbreak, at 165 0. for 00 mi .z/ m 1 1 8 Textile strength kg. cm. 20 9residual elongation, etc.), although mixes d and e have Elongation atbr'eakmmenh 720 460 475 a concentration of the diperoxide of the presentmven- Modulus at 300%,k em. 31 105 105 tion which is only 50% of theconcentration of the con- Resldualeltmgatlon at 25 8 8 ventionaldiperoxide (mix c) or of the monoperoxide (mix a).

The products of mix b, on the contrary, have a very EXAMPLE 10 lowdegree of vulcanization as compared with those ob- 40 tained from mixesa, c, d and 2, since mix b contains a conventional diperoxide (Varox)with a concentration corresponding to 50% of that used in the comparisonmix a. This shows that when using the same molar con- From anethylene-propylene copolymer containing 51% by mols of propylene andhaving a viscosimetric average molecular weight of 132,000, thefollowing vulcanized products were prepared and tested as described inExam 1e 7 centration of a conventional diperoxide (Varox) and of p Partst i lf i i p p f f t j z. ig Ethylene-propylene copolymer 100 g ii g zfi as lg e case 0 e Peron es Carbon black HAP a on bis tert.but l eroxdiiso ro lbenzene From an examination of the results reported in Table(0 0048(1 P y) p py 1 63 1, columns 1, g, h and i, in which the mixes donot con- 50 Sulfur Varying tain sulfur, with the results in columns c,e, d and a, respectively, it can be seen that the diperoxides of thisin- The results using different amount of lf are vention have muchgreater vulcanizing effectiveness in ported in Table IV. the presence ofsulfur and that the presence of sulfur in the mix improves thecharacteristics of the vulcanized TABLE Iv products.

Analogous results were obtained also with the diperox- Sum, ides ofExamples 4 and 5.

Gram- Residual EXAMPLE 8 atomsper Tensile Elongation Modulus elongationParts mole of strength, at break, at 300%, at 200, From anethylene-butene copolymer containing 34% Percent PBI'OXIdB e/ pe a/percent by mols of ethylene and having a viscosimetric average M0 122430 21 molecular weight of 142,000, the vulcanized products de- Hg 8-8g8 1g scribed in Table II were obtained, by operating as de- 201 410 1247 scrib d i Example 7, 0.25 1.62 215 400 132 6.5 0. 30 1. 94 210 425 12s7. 5 TABLE II 0. 40 2. 50 204 430 102 8 0. 50 a. 24. 205 470 97 s. 5Ethylene-butene copolymer, g 100 100 100 0.60 3. 88 202 540 93 9 Carbonblack HAF, g 50 0.80 5. 18 209 610 67 11 Sulfur, gram-atoms 0. 004810.00962 0. 00062 1.00 6. 43 193 700 54 13 Cumyl peroxide, mols 0.004810.00962 ,a'-bis(tert. butylperoxy) diisopropyl- 7Q benzene, molsni.gnfinfi a 0.00481 Characteristics 0 e pro uc s, eanize at 3.0w 403%? 2128 193 201 EXAMPLE 11 '1 stren .crn. El diiga tiona lges, ercgnt. s figi411? n e -p py pg y g g z p q g Modulus at 300 y a 0111' e o owln mixeswere re are an en camze Residual elongation at 200%,percent.-. 22 7.5 7g p P 75 and tested as in Example 7.

a b c d e f Copolymer, parts 100 100 100 100 110 100 Clay, parts 100Carbon black HAF, parts- Carbon black EPC, parts- SiO (Ultrasil), partsMagnesium dioxide,parts Diphenyl guanidinc, parts Diethylene glycol,parts Liquid polybutadiene (Buna 32), parts" Divinylbenzene, parts 40p-Quinonedioxime dibeuzoate, parts Sulfur, parts 0. 24 0. l0a,a-bis(tert.buty1 peroxy)-diisopropylbenzene, parts. 1. 2 0.8 1. 25 1.25 vulcanization temperature, C 160 160 165 165 vulcanization time,minutes. 40 30 30 Tensile strength, kg./cm. 135 140 165 Elongation atbreak, ereent. 600 500 370 Modulus at 300%, kg. em. 30 41 132 Residualelongation at 200%, percent EXAMPLE 12 By reacting, as in Example 1,tert. butyl hydroperoxide with a hydrocarbon mixture containing 41.7% ofparadiisopropylbenzene and 57.8% of meta-diisopropylbenzene and byeliminating the volatile substances, there was obtained a mixture of thecorresponding isomeric diperoxides, a, a'-biS (tert.butyl peroxy)diisopropylbenzene, having an active oxygen content corresponding to adiperoxide concentration of 65%. On the basis of this content, 2.5 g. ofsaid mixture were added to a mix containing 100 g. of theethylene-propylene copoly-rner used in Example 7, 50 g. of HAF carbonblack and 0.25 g. of sulfur.

The mix obtained was vulcanized in a press at 165 C. for 40 minutes. Thevulcanized product, tested as in Example 7, had the followingproperties:

Tensile strength, kg./cm. 190

Elongation at break, percent 420 Modulus at 300%, kg./cm. 116

Residual elongation at 200%, percent 7 EXAMPLE 13 This example is givento show that the conventional diperoxides which do not have thestructure of the diperoxides used in this invention, i.e., do not haveboth of the peroxidic radicals bound to tertiary carbon atoms, act inthe vulcanization as monoperoxides and have a very low vulcanizingefiiciency.

A mix was prepared consisting of:

Ethylene-propylene copolymer100 g. HAF carbon black50 g. Sulfur-0.00962gram atoms The mechanical characteristics of the vulcanized productwere:

Tensile strength, kg/cm. 30 Elongation at break, percent 800 Modulus at300%, l g./cm. 14 Permanent elongation at 200%, percent 74 It may beseen from the above values that the product was scarcely vulcanized.

A second mix was then prepared using the same quantities of ingredientsgiven above with the exception that now 0.00962 mol of the diperoxidewere used: Even with a double quantity of diperoxide, using the sameamount of sulfur, the mechanical characteristics of the vulcanizedproduct were very poor.

The following examples are presented to show the excellent resultsobtained when vulcanizing at high temperatures in a eutectic saltmixture. In these examples, the vulcanizations were performed for thetimes and temperatures indicated in the tables by passing an extrudatecomprising the mixture set forth in the examples through a Hiteceutectic salt mixture comprising 40% NaNO;, 7% NaNO and 53% KNO EXAMPLE14 The following mixture was extruded and then vulcanized under theconditions and with the results set forth in Table V by passing theextrudate through a eutectic salt mixture for the times and at thetemperatures indicated.

Parts by wt. Ethylene-propylene copolymer having a propylene content of45% by mols and a viscosity ML (1'+4)100 C.=35 100 FEF carbon black 7O2,2,4-trimethyl-1,2-dihydroquinoline polymerized 0.5 Caloxol W-3 15Sulfur 0.35

u,oz'bls (tert.butylper0xy) diisopropylbenzene 2 1 Commercial roduct ofJohn & E. Stur e Ltd. B1s(tert.butyl peroxy)durene0.0048l mol 55 p g P rnt 0:10 and was vulcanized by heating at 165 C. for 40 minutes.2.233353%, 3

TABLE V vulcanization in molten salt mixture 1a 2a 3a 4a 5a 6a 1b 2b 3b4b 5b 6b Vulcamzation time, seconds 30 60 240 360 30 60 90 120 240 360vulcanization temperature, 0.

Tensile strength, kglcmfi 120 142 140 136 134 143 140 137 131 135 131137 Elongation at break, ercent 425 310 320 325 320 325 330 335 325 325345 335 Modulus at 200%, kg. cm. 89 137 142 128 128 136 131 126 119 127116 126 Permanent elongation at 200%, percent l2 0 8. 5 9. 5 10 10 9. 59 10 10. 5 10. 5 11 vulcanization in molten salt mixture 1e 2e 3e 4e 5c60 1d 2d 3d 4d 5d 6d vulcanization time, seconds 30 60 00 120 %0 360 3060 90 120 240 360 vulcanization temperature, C.

Tensile strength, l g./crn. 139 134 132 131 132 138 133 129 121 122 119Elongation at break, percent 330 330 355 345 335 350 330 350 345 365 350365 Modulus at 200%, kg./ern. 130 124 116 117 120 117 127 110 116 105108 102 Permanent elongation at 200%, percent 10. 5 11.5 12 11 11 11.510.5 11.5 11.5 13 14 13.5

13 EXAMPLE 15 The following mixture was extruded and then vulcanizedunder the conditions and with the results set forth in prepared Ethlnero 1e c 01 er Table VI by pass ng the extrudate through a eutecticsalt n 3 3, 2}? g 2% mixture for the times and at the temperatureslndicated. P9 9 91mm dlbenma .n 1 1 5 a,uL-l'J1S (tert.butylperoxy)-drisopr 0.8 Parts by Wt. Zfi-bisfiumyl pleroxgpiggimgirgpyiobergzene, g. 1.1

81 V 0811128 011 a 01. m [1.1 Ethylene/ propylene (46% by mols)/5-methyl4,7,8,9 Tensile StmgtmkgJcm, 175 m tetrahydromdene (2% by [11015)ML(1+4) at 100 Elongatlon at break, are 340 360 C 70 Modulus at 300%,kg. em. 115 109 Residual elongation. at 200%, percent 10 11Polyalkylbenzene (Preadlx 8) 10 FEF carbon black 70 EXAMPLE 1g ZnO 5Stearic acid 05 From the ethylene-propylene copolymer of Example 8,Caloxol W42 15 the following mix was prepared and then vulcanized andhandled as described in Exam 1e 6: Sulfur 0- 15 p cc,a'-biS(tert.butylperoxy)dnsopropylbenzene 2.1 Ethylene-propylenecopolymer--l00 parts 1 Ptilyalkylbenzene-Commercial product ofI.C.I.R.-Tug lil i l 1 l ?i pasts 1 l rine, taly. en en ima eimi e .0 mo-4 ar See footnote 1, column 12. p p y (0 5 P 115 TABLE VI vulcanizationin molten salt mixture 1a 2a 3a 4a 5a 6a 1b 2b 3b 4b 5b 6b vulcanizationtime, seconds 30 120 240 360 30 60 90 120 240 360 vulcanizationTemperature, 0.

Tensile strength, kgJem. 128 134 142 138 133 137 133 141 129 138 128 124Elongation at break, percent. 350 270 270 275 275 275 270 295 275 290290 310 Modulus at 200%, kgJcmfl-.. 76 108 102 98 102 100 96 95 96 88 81Modulus at 300%, kg./ern. 118 Permanent elongation at 200%, percent 9- 5R 7. 5 6. 5 7 7 7. 5 7. 5 8 7. 5 7 7. 5

vulcanization in molten salt mixture 1c 20 3e 40 50 6c 1d 2d 3d 4d 5d 6dvulcanization time, seconds 30 60 90 120 240 360 30 60 90 120 240 360Vulcanization temperature, 0.

Tensile strength, kgJCm. 139 138 129 135 127 129 124 130 122 118 119Elongation at break, percent. 275 285 280 305 285 335 305 310 315 335315 355 Modulus at 200%, kg./cm. 101 98 91 92 80 80 80 81 75 75 66Modulus at 300%,kg./cm. 133 121 124 121 125 117 114 105 Permanentelongation at 200%. percent 7 8 8 7.5 7.5 9 7.5 7.5 8 9.5 8.5 9. 5

EXAMPLE 16 out bis(tert.butylperoxy) diisopropylbenzeue (0.015

This example illustrates the higher vulcanization rate and greatervulcanization efiiciency achieved by using a diperoxide in accordancewith the present invention (11,0!-bis(tert.butylperoxy)diisopropylbenzene) in the vulcanization of a lowunsaturation terpolymer as compared to using an equimolar amount of aprior art diperoxide (2,5- bis(tert.butylperoxy)-2,5-dimethylhexane) atthe same temperatures.

The following mixtures were vulcanized for the times and under theconditions set forth in Table VII, the remol)-0.5 1 part Aftervulcanization at 165 C. for 30 min.:

Tensile strength, kg./cm. 186 Elongation at break, percent-390 Modulusat 300%, kg./cm. 125 Residual elongation at 200% percent-11 EXAMPLE 19The following mixture was extruded and then vulcanized under theconditions and with the results set salts being set forth in the lowerportion of Table VII. 55 forth in Table VIII by passing the extrudatethrough a TABLE VII Ethylene/propylene (43 molpercent)l5-methyltetrahydroindene (4.3 mol percent) terpolymer ML(1+4)100 C.=65 75 70 Polyalkylbenzene (Preadix 8) 30 30 HAF carbon black 6060 Sulfur. 0. 4 0. 4 a,a-bis(tert.buty1peroxy) diisopropylbenzene 2. 12,5-bis(tert.butyl peroxy)-2,5-dimethylhexane 1.8 Vulcanizationconditions Injection press at 200 C. Injection press at 200 C.

Time, minutes 40 0. 5 1 2 4 6 10 60 0. 5 1 2 4 6 10 Tensile strength,kgJcrn. 175 168 165 164 168 158 158 169 120 153 147 137 137 Elongationat break, perce 270 400 325 300 360 860 375 515 580 620 660 665 670 675Modulus at 200%, kg./cm. 114 53 64 72 63 59 53 43 25 28 27 v 23 21 20ISO hardness- 69 60 65 65 64 63 63 63 63 55 55 55 54 55 1 Plate press at0.

EXAMPLE 17 From the ethylene-propylene copolymer of Example 7,

eutectic salt mixture at the temperature of 250 C. for the timeindicated.

TABLE VIII.VULCANIZATION IN MOLTEN SALT MIXTURE vulcanization time(seconds) Tensile strength, kg./cm. 110 135 140 145 140 Elongation atbreak, percent 240 210 225 250 240 Modulus at 200%, kgJem." 87 120 114110 108 Permanent elongation percent at 200%.... 5 5 5 5 5 EXAMPLE Thefollowing mixture was vulcanized under the conditions and with theresults set forth in Table IX by vulcanizing in an injection press at220 C. for the time indicated.

Parts by weight Ethylene/propylene (46% by mols)/5-methyl-4,7,8,9-

tetrahydroindene (4%) ML (1+4) at 100 C. =75 70 Polyalkylbenzene(Preadix 8) HAF carbon black 60 Sulfur 0.4 a,a-bis(tert.butylperoxy)diisopropylbenzene 2.1 a,a'-Bis(tert.butylperoxy) diisopropylbenzene 2.1

TABLE IX.IN.TEOTION PRESS From anethylene/propylene/S-methylen-norbornene terpolymer containing 41% bymols of propylene and 3.1% by mols of S-methylen-norbornene and having aMooney viescosity of 91 ML (1+4) at 100 C. the following mix wasprepared in a roll mixer:

Parts by wt.

Ethylene/propylene/S methylen norbornene terpolymer 100 SRF carbon black60 Sulfur 0.16 c d-bis(tertbutylperoxy)diisopropylbenzene 1 This mix wasvulcanized by heating at 165 C. for

minutes.

The mechanical characteristcs of the vulcanized product were:

Tensile strength, kg./cm. 130 Elongation at break, percent 380 Modulusat 300%, kg./cm. 102

Permanent elongation at 200%, percent 12 16 EXAMPLE 22 The followingmixture was vulcanized in an injection press at 210 C. for 5 minutes:

Parts by wt.

Ethylene/propylene (44% by mols)/dicyclopentadiene (3.8% bymols)terpolymer ML (1+4) at C.=73 100 HAF carbon black 50 Sulfur 0.160:,04' bis(tert.butylperoxy)diisopropylbenzene 1 The mechanicalcharacteristics of the vulcanized product were:

Tensile strength, kg./cm. 176 Elongation at break, percent 475 Modulusat 300%, kg./cm. 94 Permanent elongation at 200%, percent 14.5

Variations can, of course, be made without departing for the spirit andscope of the invention.

Having thus described our invention, what we desire to secure by LettersPatent and hereby claim is:

1. A vulcanizable composition comprising (1) a vulcanizable saturatedelastomeric copolymer of ethylene with a higher alpha-olefin having theformula CH =CHR in which R is a lower alkyl radical, said copolymerhaving an ethylene content of from about 5 to 70 mol percent themolecular weight of said copolymer being between about 60,000 and800,000; (2) a diperoxide having the general formula:

in which R to R inclusive, are selected from the group consisting ofunsubstituted and halogen-substituted lower alkyl radicals, R and R areselected from the group consisting of unsubstituted and substitutedalkyl radicals containing from 1 to 6 carbon atoms and unsubstituted andsubstituted aromatic radicals containing from 6 to 20 carbon atoms, andA is an arylene radical selected from the group consisting of phenylene,diphenylene, anthrylene and naphthylene, in a concentration of fromabout 0.002 to 0.02 mols of diperoxide per 100 grams of saidvulcanizable copolymer; and (3) a radical acceptor selected from thegroup consisting of sulfur, quinone compounds and dimaleimidiccompounds, in a concentration of from 0.1 to 20 grams per 100 grams ofthe vulcanizable copolymer.

2. The vulcanizable composition of claim 1 wherein the radical acceptoris sulfur.

3. The vulcanizable composition of claim 2 wherein the sulfur is presentin a concentration of between 1.6 and 2.0 gram-atoms per mol of thediperoxide.

4. The vulcanizable composition of claim 1 wherein the vulcanizablepolymer is an ethylene/propylene co polymer.

5. The vulcanizable composition of claim 1 wherein the vulcanizablepolymer is an ethylene/butene copolymer.

6. The vulcanizable composition of claim 1 wherein the diperoxide isselected from the group consisting of a,u'-bis(tert.butylperoxy)diisopropylbenzene and mabis (cumyl peroxy diisopropylbenzene.

7. A process for vulcanizing the composition of claim 1 which compriseshomogenizing said composition and vulcanizing it at a temperature offrom about to 260 C. for a time of from about 30 seconds to about 6hours.

8. The process of claim 7 wherein said composition is vulcanized at atemperature of from about to 200 C. for a time of from about 30 minutesto about 4 hours.

9. The process of claim 7 wherein said composition is vulcanized at atemperature of from about 200 to 17 250 C. for a time of from about 30seconds to about 6 minutes.

10. The process of claim 9 wherein the vulcanization is performed bypassing an extrudate of said composition through a eutectic salt mixturemaintained at said temperature, said eutectic salt mixture comprisingabout 40 weight percent NaNO about 7 weight percent NaNO and about 53weight percent KNO 11. The process of claim 7 wherein said compositioncomprises a diperoxide selected from the group consisting ofa,a'-bis(tert.buty1 peroxy)diisopropylbenzene and a,u'-biS (cumylperoxy) diisopropylbenzene.

12. The process of claim 11 wherein said composition further comprises acopolymer selected from the group consisting of ethylene/propylene andethyIene/butene copolymers.

13. Molded and extruded articles of vulcanized elastomers obtained byculcanizing the composition of claim 1.

14. The composition of claim 1, said composition additionally comprisinga reinforcing filler.

15. The composition of claim 14, wherein said filler is carbon black.

1 8 References Cited UNITED STATES PATENTS FOREIGN PATENTS 11/ 1964Great Britain. 6/ 1963 Great Britain.

MURRAY TILLMAN, Primary Examiner C. I. SECCURO, Assistant Examiner US.Cl. X.R.

E22 2? UNITED STATES PATENT OFFECE CERTIFICATE OF CGRRECTION Patent No.3,522,225 Dated July 28, 1970 Invent0r($) Cesare Augusto Peri et al Itis certified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Column 1, after line 13 and before line 14, insert the followingparagraph:

-C3.aims priority, applications Italy, December 22, 1960 21,949/60 andSeptember 27, 1961, prov. 16,600.

Signed and sealed this 12th day of June 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR.

ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents

